IN THE spirit of the political season, I recently watched Robert Redford’s movie “The Candidate,’’ first released in 1972. The film is a satire - gentle by today’s standards - of our electoral system, in which an idealistic young lawyer named Bill McKay (Redford) is persuaded to run for US Senate, losing his innocence even as he wins office. McKay’s frustrations with the hypocrisy and absurdity of campaigning ring true today. But the real value of this cultural artifact is the lens it provides on the country’s ideological shift over the past 40 years.

Both McKay and his conservative opponent Crocker Jarmon - a powerful incumbent who doesn’t realize the times they are a-changin’ - are broadly drawn caricatures in the original screenplay. But the conservative’s statements in the film are squarely in the mainstream of Republican political dialogue today, while the liberal’s views now seem hopelessly far out. When the censorious Jarmon fumes about the threats to America from “a collectivist state,’’ when he says “We’re going to tell Big Brother to get lost,’’ when he sheds a crocodile tear over visiting the L.A. Rams’ locker room and “seeing all those big tough guys down on their knees in a simple moment of prayer,’’ nothing clangs or seems awkward.

After all, Mitt Romney has attacked President Obama for plotting to create “a European-style welfare state.’’ One of his favorite phrases is “It’s time for big ideas, not Big Brother.’’ And we have all become accustomed to ostentatious displays of piety among the Republican presidential hopefuls.

The cinematic McKay’s liberal views, on the other hand, seem as outdated as the wide sideburns and saucer-shaped eyeglasses on his campaign handlers. Asked if he supports welfare, he says: “We subsidize trains, we subsidize planes, why not people?’’ When he tours Watts, he says the government is failing the people because there is “no hospital; no birth control center.’’ He proposes to “take some of the oil and gas taxes and clean up’’ a polluted harbor. It’s not just campaign rhetoric but real public policies that have left McKay behind.

“Subsidizing people’’ on welfare went out with Bill Clinton in 1996. Most of the Republican candidates have pledged to cut off funding for Planned Parenthood, and Rick Santorum opposes birth control (not just abortion) because “it’s a license to do things’’ that he objects to. As for oil and gas taxes, what taxes? The group Taxpayers for Common Sense has reported that oil and gas industries will receive nearly $80 billion in tax breaks and subsidies over the next five years. The rightward shift of the political center has been a little like the famed frog in a pot of slowly boiling water: imperceptible at first.

When “The Candidate’’ came out in 1972, Republican Richard Nixon was president - and he created the EPA, imposed price controls, introduced a “full-employment budget’’ built on deficit spending, pushed national health insurance, and negotiated with Communists. Would any Republican candidate dare suggest such policies today?

Conservative ideologues have steadily infiltrated the Republican Party, and it has grown increasingly intolerant of compromise, giving no quarter on policy or process. President Clinton supported center-right policies such as free trade, welfare reform, and (disastrously) financial-sector deregulation. But any similar nods to the center on the Republican side - on climate-change solutions, perhaps, or closing tax loopholes - are beyond consideration.

And where has 40 years of relentless rightward pushing and tugging left us? The country’s public institutions are defunded, deregulated, and delegitimized. Budgets are slashed; desperate communities turn off their streetlights or sell advertising space on the sides of police cars to raise cash. Republicans refuse even to consider confirming a Nobel Prize-winning economist for an important financial post. Income inequality is the greatest it has been since the 1920s.

One other thing happened in 1972: Nixon was reelected, and Democrats suffered one of the worst presidential drubbings in history. The youth vote and anti-war activists had all the intensity, but they couldn’t replace mainstream moderates who felt alienated from a culture many found extreme. Now the shoe is on the other foot. Americans don’t like extremists, and they may reject the unyielding forces of the right. Let’s hope so, before gridlock seizes Washington permanently, and the screen fades to black.

Renée Loth is editor of ArchitectureBoston magazine. Her column appears regularly in the Globe.